The direct gas fired industry has had some significant changes in listing
requirements over the past few years. One of those changes was to the
ANSI Z83.18 standard for Re-circulating direct gas fired heaters. Under
this new standard, one of the restrictions is the amount of heat
(temperature rise) you can add to the space, based on percentage of fresh
air that is introduced into the building. After hours of research, design
and testing, our engineering team came up with a
new control system that will be used to meet this new requirement. This
new control system has been designed with our customer's safety, ease of
service and economics in mind. The name of the new control system is the
RCS System which is an acronym for "Re-circulating Control System".

The RCS System monitors return air temperature, fresh air temperature,
will limit return air damper percentage, and will limit maximum discharge
temperature. There are different RCS Systems available to best fit your
application. Below is a chart on the different RCS Systems to pick from.

How to pick the RCS System for your Application

What is your minimum Winter Design Condition? Use the chart below to see which system qualifies: if Minimum Outdoor Air Temperature is above temperature listed on chart, that system qualifies.

What is your Minimum Indoor Air Temperature? Look at qualified systems available (after step one) to see which system qualifies to meet this requirement.

After step one and two, your qualified system may be down to one selection; if not, you now have the choice of picking the system that best fits the application.

Note: Always pick the RCS System closest to your minimum temperature
conditions for best performance.

Re-Circulating Heater Control Systems

RCS System

Minimum Outdoor Air Temperature

Minimum Indoor Air Temperature

Maximum Recirculation Percentage

Maximum Discharge Temperature

RCS5

-30°F

7°F

60%

90°F

RCS10

-30°F

25°F

50%

120°F

RCS15

-25°F

58°F

80%

90°F

RCS20

-25°F

54°F

60%

120°F

RCS25

-20°F

55°F

50%

140°F

RCS30

-15°F

47°F

60%

120°F

RCS35

0°F

52°F

80%

90°F

RCS40

0°F

35°F

50%

140°F

How does the RCS System work?

The Re-circulating heater will modulate the return air and fresh air
bypass dampers based on the damper control selected: two-position,
photohilic, or manual potentiometer. The RCS System is designed to
limit percentage of return air and discharge temperature based on the
system selected as shown in the chart above. If the temperature drops
below minimum set points, the bypass dampers will drive to 100% fresh air
for a short time until minimum set points are satisfied. Once the trip
minimum set point is satisfied, the bypass dampers will return to normal
operation.

It is important when sizing and designing your Re-circulating
heater to select the RCS System that best meets the application.
When ordering a Re-circulating system, please specify the RCS system
you would like to use; otherwise, a RCS system will be selected for you.